Pulldown cylinder assembly for mast slides



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Sept. 25, 1951 Sept. 25, 1951 f n .`c.. bANlELs I 2,569,126

PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES vFiled oct. 2o, 1949 ssheets-sheet 2 INVENTOR. 5E C. DAN/ELS Arfogwfr Sept. 25, 19,51

L. C. DANIELS PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES Filed Oct. 20,1949 INVENToR, 5 c. DAM/L5 BY v ff ig Patented Sept. 25,1951

PULLDOWN CYLINDER ASSEMBLY FOR MAST SLIDES Lee C. Daniels, Cleveland,Ohio. assignor to Towmotor Corporation, Cleveland, Ohio, a corporationof Ohio Application October 20, 1949, Serial No. 122,476

1 This invention relates broadlyto lift trucks, and more specifically toimprovements in the mechanism employed to effect the retraction of themast slide.

In detail, the invention pertains to lift trucks of the type that areprovided with a mast having an extensible slide thereon, a ram for,theelevation thereof, and a carriage on the slide mounted for limitedreciprocative movement relative thereto. In such structure it iscustomary to interlink the ram with the slide to assure the descentthereof during the retraction of the ram and to provide a lost-motionconnection in the linkage to facilitate the action of the free liftmechanism for the carriage during the initial elevation of the ram. Anobjectionable characteristic of the lost-motion mechanism resides in thefreedom of the slide to Vdrop under the influence of gravity lwheneverthe tensive strain on the pulldown linkage is relaxed, as occurs instacking, dock loading, and similar operations when the carriage isbrought to rest during the descent of the slide, but before the pulldownlinks have traversed the escapement plate of the lost-motion mechanism.i I

The present invention eliminates the foregoing objection through theprovision of a piston cylin der assembly disposed between the top of theslide and the cross-head on thefree end of the` ram, the assembly beingdesigned to pull the slide down during thedescent of the ram and snubthe free movement thereof whenthe tension on the piston rod is released.

Further objects of the invention reside in the provision of aslide-retracting mechanism'which may be assembled within the hydraulicram, a structure which will cushion the shock upon the slide when themovement of the ram is reversed, a device to retard the sudden descentof the slide when the load is removed from the carriage While in anelevated position, and an assembly which is eincient of operation,durable of structure, and economic of manufacture.

Other objects and advantages, more or less ancillary to the foregoing,and the manner in which all the various objects are realized will appearin the following description, which, considered in connection with theaccompanying drawings, sets forth the preferred embodiment of theinvention. Y

In the drawings:

Fig. 1 is a vertical sectional view of a fragmentary portion of a lifttruck mast embodying the improved slide-retracting mechanism, Vthe slidebeing illustrated in its lowered position;

6 Claims. (Cl. 187-9) Fig. 2 is a front elevational view of the mastillustrating the position of the parts thereof during the ascent of theram;

Fig. 3 is a similar elevational view illustrating the position of theparts of the assembly during the descent of the slide;

Fig. 4 is a similar elevational view showing the carriage `in anelevated position (resting on a platform with the load releasedtherefrom) and the mast slide in a partially retracted position; and

Fig, 5 is atransverse sectional view of the upper portion of the ram andassociatedV parts of the assembly, the section being taken on a planeindicated by the line 5-5 in Fig. 1.

Referring first to Fig. 4. the lift truck chosen herein for the purposeof illustration comprises a motor propelled vehicle I0 having a mast IIon the forward end thereof, an extensible slide I2 mounted thereon, aload-carrying platform I3 associated with'the slide, and a hydraulic ramI4 for raising and lowering the slide. The loadcarrying platform ismounted on a carriage I5 which is organized for limited reciprocativemovement along the slide during the initial movement of the ram. The ramis constructed with a cross-head I6 on the free end thereof, a pair ofsheaves I1 carried thereby with chains I8 roved thereover, which areanchored at one end to the mast and at the other end, to the carriage.The side rails of the slide are united at their upper ends by a crossmember I9 which is disposed for engagement with the cross-head duringthe ele-KV vation of the ram, but spaced therefrom when the slide andram are in their lowered position (Fig. l). With this construction theinitial movement of the ram will elevate the sheaves and pull thecarriage upwardly until the cross-head engages the cross member I9;thereafter the chains willi merely roll over the sheaves during theremainingv elevation of the ram. When the ram is retracted the slidewill normally descend therewith underthe influence of gravity, theweight thereof being; borne by the head of the ram until the slide is;brought to rest by engagement of the cross mem-- ber I9 with the upperends of the mast.' Frequently, however, when the engaging surfaces ofithe mast and slide are worn or improperly lubricated, the slide willcock during the descent of:

is machined for snug sliding movement Withinv The ring 24 isdisposed-for" abutting engagement with the cross-head I6, the lowery thenut 22.

face thereof being bored for theireeption of a tube 25 constituting asupporting Ame'rnjber for the lower end of a hydraulic shock absorber26.

The cap or end wall of the lower end ,of the when the ram is brought torest when the tension on the flexible connections is relaxed.

43. I n a 'lift truck embodying a mast having 'a' slide thereon, and ahydraulic cylinder having 4a hollow` piston `therein disposed forabutting shock absorber is formed withan eye r21 forthe reception of awrist pin 28 which is seated aligned cross bores adjacent the free endof the tube 25. The shock absorber is of conventional form, embodying apiston 29 which is formed with restricted openings 30 therein to ypermitthe ow of fluid from one side of the piston to the other. The cross-headI6 is bored for the rec'eption of the end portion of the shocl; absorbercylinder, and the outer end of the piston rod 3| is provided with an eye32 having a wrist pin 33 therein which is supported in lugs 34afxed toand depending from the lower face of the slide cross member. The freeends of the lugs 34 are notched (Fig. 4) to clear the shock absorbercylinder cap 35 when the slide is in its fully retracted position.

In operation, when the motive fluid is introduced into the ram cylinder20, the piston 23 will be distended and thus cause the elevation of thecarriage I5 until the cross-head engages the lugs 34; whereupon theslidewill be elevated as shown in Fig.- 2. During the descent of the ram, thepiston .rod 3| will pull-the slide downwardlynntil the movement thereofis arrested by the engagement of the cross member I9 with the end ofvthe mast 26. As the shock absorber piston rod is distendedv during thedescent of the slide, the oil will flow through the restricted openings30 in the piston, and thus cushion the shock imposed uponthe crossmember.

When the'carriage is brought to rest before the load-carrying platformreaches its lowermost position, as occurs in .stacking operations (Fig.4), the tension on the chains I8 and shock absorber piston rod 3l willbe relaxed; and the weight of the slide will be imposed ,upon theextended piston rod and effect the reversal of flow of the fluid throughthe opening 30 in the-piston, thus snubbing the sudden descent of theslide.

Although the foregoing description is necessarily ofva detailedcharacter, in order that the invention may be completely set forth, itis to be understood that the specic terminology is engagement with theslide for the elevation thereof, mechanism for retracting said slide andsnubbing the descent thereof comprising a tube amxed within the free endof the hollow piston, a hydraulic shock absorber cylinder supported inthe lower end of said tube, a piston in said shock absorbercylinder`.connected to said slide, and a cap on said shock absorbercylinder engaged with said vpiston during the initial descent of saidhollow piston.

. 4. Mechanism for the retraction of a poweractuated mast slide in alift truck comprising a hydraulic piston cylinderassembly constituting aslide pulldown member and a shock absorber, one of the parts of saidassembly being attached to said slide, and the other part'of saidassembly being attached to the power-actuating mechanism for the slide,whereby said slide will be pulled downwardly during the initial movementof the power actuating mechanism for the slide and subsequent movementthereof will be retarded.

5. In a lift truck embodying a mast, a slide mounted for reciprocativemovement therein, a hydraulicram piston for elevating the slide, and across-.head on the free end of the piston, mechanism to pull vthe `slidedownwardly comprising a member aiiixed to'and depending from thecross-head, a hydraulic shock absorber cylinder connected thereto, asecond member afxed to and depending from the slide, and a hydraulicshock absorber piston connected to the last-named member.

6. In a lift vtruck embodying a mast, a slide frame thereon and ahydraulic ram plunger arranged 'for abutting engagement with the slideframe, mechanism for retracting the slide frame comprising a hydrauliccylinder, a cap on the bottom thereof pivotally connected to saidplunger, -a cap-on the top of said cylinder, a piston-in said cylinderengageable with the cap on the top of the cylinder, a piston rod on saidpiston protruding v,through the cap on the top of .the cylinder, saidpiston rod being pivotally connected 'to said slide frame, said cylinderbeing mounted so thatA the piston will be disposed adjacent the vcap onthe bottom of the cylinder when the ram plunger is in its loweredposition and will engage the cap on-the top of the cylinder during thedescent of the ram plunger.

LEE C. DANIELS.

REFERENCESV CITED The Ufollowing references 'are of record'in the flleof this patent:

UNITED STATES PATENTS Number 2 ,419 ,9.38

